Chemical Engineering
Laboratory 1
Ch.E. 333.2
Laboratory Manual
W2012_T2
Course Outline
I.
PURPOSE OF THIS COURSE
This course is intended to develop skills, which will be of use to you as a practicing
chemical engineer. You will be expected to use typical items of equipment and to conduct
simple measurements and tests. You will be expected to communicate the results in a clear
and effective manner.
II.
ORGANIZATION OF THE COURSE
1. Data Recording*
Each student in the course must have a hard-cover laboratory notebook. Experimental
investigations will be conducted in groups of two or three students. One student from
each group will be designated to be responsible for planning the investigation (this
task is described more fully below). All students are responsible for:
a) Visits to the laboratory to view the apparatus and discussions with the instructors.
b) Producing a notebook record of what was done in the laboratory. This will be
signed by the Demonstrator, who will certify that all students were present.
c) Experimental observations both quantitatively and qualitatively.
d) Preparation of a suitable apparatus diagram.
e) Sample calculations, showing how the data were used. If a technical memo is to be
submitted then the sample calculations must be in the log book.
f) Preparation of graphs and/or tables showing the salient conclusions from the
experiment as clearly as possible.
g) Preparation of formal, brief or technical report.
*refer to section VI for rules for laboratory notebooks.
2. Planning.
The designated student leader is responsible for planning the experiment and for
ensuring that sufficient data of an appropriate quality are obtained. This will require
background reading, visits to the laboratory to view the apparatus and discussion with
the instructors. All partners will be assessed for their contribution to the experiment by
the Demonstrator.
3. Reporting.
1
Each student is required to hand in one full formal report, one group presentation and
two technical memos. When one partner submits a formal report, the other partner
must submit a technical memo. Reports and memos are due two weeks from the
completion of the experiment, unless a time extension has been granted. Student will
get 7 “free” late hand–in days for the whole course. Indicate on your report when you
use it. Reports and tech memo‟s are to be handed in to Dale Claude in Room 1D43
(office inside 1D25), and marks will be deducted for tardiness (read EVALUATION
below).
III. EXPERIMENTS
1.
2.
3.
4.
5.
6.
Viscosity
Centrifugal Pump
Fluid Metering
Saturation Pressure
Heat Exchange: Double Pipe, water-water
Fluid Friction in Pipes, Valves and Fittings
Visit http://www.engr.usask.ca/classes/CHE/333/ to download LABORATORY MANUAL.
Only 4 experiments will be performed.
IV. GUIDES FOR PREPARING REPORTS
Full Formal Reports:
All formal reports must be done on a word processor. The following sections of the report
should be included:
1. Title: Course number
Name of the experiment
Students participating (group members present)
Date of Experiment
Due Date
2.
3.
4.
5.
(The template file for the title page of formal, brief and technical reports can be
downloaded under the heading of Title Pages at
http://www.engr.usask.ca/classes/CHE/333/)
Abstract: This is written after the Discussion has been completed. It may be prepared
with a word processor and pasted into the notebook. It is intended to be read by
persons who will not read the rest of the report.
Table of Content: Give titles of sections with their page numbers. This should include
the Appendix with titles of each section of the Appendix.
Introduction. This is a brief statement of the purpose of the experiment. It serves as an
introduction to the rest of the report.
Theory. A brief summary, giving the equations to be used, is required.
2
6. Apparatus and Procedure. The apparatus diagram can be prepared with a drawing
program or drawn by hand. Chemical Engineering symbols for the unit operations
should be used wherever possible so that a proper Process Flow diagram (PFD) is
prepared. The procedure should record what was done. It must not be written as
instructions.
7. Presentation and Discussion of Results: In this section, indicate where the data and
results are presented. Any significant observations should be reported here and what
effect that had on the outcome of the experiment. Data and result are probably
presented most effectively in tabular form in an Appendix. Graphs can be presented in
this section or in an Appendix. Your results should then be fully discussed in this
section. All conclusions and recommendations must be defended. Error analyses may
or may not be useful in this regard. Figures or Graphs can be included in the body
(insert as the page following the first mention of the graph in the body of the report) of
the report or presented in an Appendix. If there are several graphs that are similar, a
representative graph can be included in the body of the report.
8. Conclusions: Give your conclusions in numbered statements, each one concise and
precise. No discussion is given here. All conclusions must be fully discussed and
supported in the Discussion Section.
9. Nomenclature: List all symbols used in alphabetical order. Greek symbols should be
kept in a separate list.
10. Recommendations: A similar format to that of the Conclusions should be followed
here.
11. Reference: A list of references must be included here. Use a standard format (list in
alphabetical order and in the body of the report refer to the last name of the first author
followed by the year of publication in brackets).
12. Appendix: Identify them by A, B, C … and in the following order: data, results,
sample calculation. All tables and Figures should have headings (e.g., Table B1, Figure
A1, etc.) and full titles. In your sample calculation, indicate the run number used and
which table(s) the information can be found.
13. Constrain the length of the formal report within 20 pages.
Oral Presentation:
Each group is required to deliver one oral presentation based on the lab they have
performed. The content of the presentation should include introduction of the lab,
theories and/or principles, objectives of the lab, experimental procedures, data collection,
data processing, results and discussion, conclusion and recommendation. The duration of
the presentation is 10 – 12 minutes. All the students in the same group will work
collaboratively, and will be evaluated as a group.
Technical Memos:
A technical memo is a brief memorandum to the supervisor. It should state concisely the
experimental conditions, results, discussion, conclusions and recommendations. A brief
3
table of results or a graph should be included to support the conclusions. Limit your
technical memo within a 2-page length.
V. EVALUATION
Careful measurements, correct calculations, logical deductions and clear conclusions are
necessary to a good report. However, even if all these are present but the report is not well
written, some of the positive effects of the investigation will be lost. Although proper
spelling, grammar and general use of the English language are somewhat less important than
clarity, conciseness and technical contents, they will also have an effect on the marking.
The formal report and technical memos will be marked out of 10 grade points. However, for
the final mark, each formal report will be worth 35 marks, and the technical memo, 10
marks. The lab demonstrator will be reviewing your performance and your lab notebook
while you are in the lab and will assign a mark (out of 5) at the end of each lab period. A
summary of the marking scheme is given Table 1 below.
The formal report and technical memos must be completed and submitted within two weeks
i.e. while the experiment is still fresh in the student's mind. Therefore, the deadline for
receiving report and technical memos without any penalty will be two weeks after the
experiment was performed. A penalty of 10% per week will be deducted from late report
or memos. Submissions will not be accepted after the last day of classes and will be given a
mark of zero. The presentation slides (in power point format, preferably) must be submitted
to the lab instructor and the lab coordinator as an email attachment by March 22nd at 4:30
p.m.; otherwise a 10% penalty will be applied after the deadline. Visit
http://www.engr.usask.ca/classes/CHE/333/; click on Class Info; scroll down to Grading
Sheets; choose an appropriate marking sheet to view what will be evaluated in the submitted
report and memo.
Table 1. Distribution of Marks
Item
Full Report
Oral Presentation
Technical Memo
Lab Performance
& Notebook
Total Mark
Number Individual
Mark
1
35
1
25
2
10
4
5
Final
Mark
35
25
20
20
Penalty (10%)
3.5
2.5
1.0
100
The mark distribution is only approximate. Final grades will be assigned at the discretion of
the instructor subject to the University Council and College Regulations on Examinations.
Students should be aware of and follow the University of Saskatchewan Academic
Honesty/Dishonesty definitions, rules and procedures that are available on the web at
www.usask.ca/honesty.
4
VI. RULES FOR LABORATORY NOTEBOOKS
1.
2.
3.
4.
5.
the
Use a hard-covered and numbered record book (purchase from University Bookstore)
Label research ideas/proposal to differentiate them from experiments that are performed
Explain all abbreviations or terms that you use that are not universally known
Make all entries in ink
Do not erase any entry. Instead draw a line neatly through the error and then initial and date
correction in the margin
6. Record data and observations when they are made. Date each entry
7. Stick to the facts (positive and negative). Your notebook is not the place for your opinion
8. Leave no blank space between entries. Cancel all blank spaces (including blank pages) with
diagonal lines drawn across the space. Initial and date the cancellation in the margin
9. Have each page of your notebook witnesses by someone who is not an inventor but who
understands the experiment and its objectives (ask your Lab Demonstrator as the witness)
10. Make no changes or insertions on a page after it has been signed and witnessed
11. Attach support records to the notebook where practical. If not practical, then, cross-reference
the notebook with the material and witness as above
12. Maintain safe custody of your notebook
5
Sample of evaluation sheets
6
ChE 333 – FORMAL REPORT GRADE SHEET
Student: _____________________ Experiment: __________________
Date Due: ___/___/___ Date Rec‟d: ___/___/___ Late Penalty: _____%
REPORT SECTION
Title Page
CLARITY OF
PRESENTATION
Max. Mark
TECHNICAL
CONTENT
Max. Mark
2
Abstract
3
Table of Contents
Nomenclature
Introduction
Theory
Apparatus
Procedure
Pres. & Disc. Results
6
3
Conclusions
Recommendations
References
8
10
6
20
3
10
3
6
2
Appendices
Experimental Data
Calculated Results
Sample Calculation
6
4
4
4
Totals
36
64
Report Mark = (Total Mark) * 0.35 = ____________ (MAX = 35)
* GRADE POINT (G.P.) DESCRIPTOR *
10
9.5
Exceptional Excellent
8-9
Very
Good
7 – 7.5
Good
6 - 6.5
Satisfactory
7
5 – 5.5
Passable
0 – 4.5
Fail
ChE 333 – TECH MEMO GRADE SHEET
Student: ______________________________________
Experiment: ______________________________________
Date Performed: ___/___/___
Due Date: ___/___/___ Date Rec‟d: ___/___/___ Free Late Days: ___
Late Penalty: ___ %
MAX
PRESENTATION

Title page……………………………...
5

Purpose clearly stated…………………
5

Experimental conditions & constants
clearly stated…………………………..
5
Apparatus, procedure, conclusions, &
recommendations content…………......
15

READABILITY

Spelling & grammar…………………..
10

Sentence & paragraph structure/ clarity
10

Logical sequence & cohesiveness of
writing…………………………………
10
TECHNICAL CONTENT (RESULTS)

Presentation & correctness……………
20

Discussion & interpretation…………...
20
Total
100
8
MARK
EXPERIMENTS
1.
Viscometry
Introduction
This experiment involves the use of a cone and plate viscometer. You will be asked to
characterize a fluid which may or may not be Newtonian. Newtonian fluids should be tested at
different shear rates for a range of temperatures. Non-Newtonian fluids should be tested at a
range of shear rates. Discuss the choice of a fluid with the instructor before planning the
experiment.
Procedures
The viscometers are operated empty at first to find deflections at zero load. The viscometers
must be operated according to the procedures in the literature provided in the laboratory.
Because they are sensitive and expensive instruments, please read the procedures carefully
before operating them. If you are unaware about any procedure, ask the demonstrator before
proceeding. When you are placing the fluid in the viscometer, try to avoid entrapping air
bubbles as these may cause significant errors. Also, before changing fluids in a viscometer,
wash it thoroughly since small amounts of contamination may distort the results. Be careful not
to scratch the surfaces of the measuring elements.
Before testing an unknown fluid, a Newtonian standard fluid should be used to verify instrument
performance.
Data
1. Brookfield Viscometers (springs are linear)
(i) LV, full scale deflection = 673.7 dyne-cm
(ii) RV, full scale deflection = 7187 dyne-cm
(iii) Cone Angle,  = 0.8 degrees
(iv) Cone Radius, r = 2.4 cm
(v) Cone and Plate, sample = 0.5 ml
2. Working equations:
9
i)
Cone and Plate
 ( dyne / cm 2 ) 
 (sec 1 ) 
where
3T
2r 3

sin 
 = shear stress ( dynes/cm2)
 = shear rate ( sec -1)
T = torque (dyne-cm)
 = angular velocity of the spindle (rad/sec)
 = cone angle (degrees)
r = cone radius (cm)
Characterizing a Fluid:
For Newtonian fluids, comment on the effect of temperature upon viscosity by
comparing your results with those predicted by the Eyring theory(4) . For nonNewtonian fluids, select a suitable model and evaluate the coefficients in its equation of
state relating shear stress to shear rate.
For non-Newtonian fluids calculate the pressure drop per meter of pipe in horizontal
flow if the velocity is 1.0 m/s and the pipe diameter is just small enough to ensure
laminar flow (i.e., the flow is not turbulent).
References
1.1 Streeter, V.L., “Handbook of Fluid Dynamics”, Chapter 7. McGraw-Hill Book Company
Inc., 1961.
1.2 Middleman, S., “The Flow of High Polymers”, Interscience Publishers, 1968.
1.3 Cheremisinoff, N.P. and Gupta, R., “Handbook of Fluids in Motion”, Ann Arbor Science,
1983.
1.4 Tabor, D., “Gases, Liquids and Solids”, 2nd Ed., Cambridge Univ. Press, 1979.
10
2.
Centrifugal Pump
Objectives:
a)
To determine the characteristics of a centrifugal pump including total head, power,
efficiency and NPSH versus flowrate.
b)
To determine the size of a geometrically similar pump that would be needed to pump
against a total head of 100 feet of water at peak efficiency using the same RPM.
Introduction:
Centrifugal pumps are the most common type of fluid mover in the chemical industry. A
fundamental understanding of the operation and performance of a centrifugal pump is of primary
importance to any engineering student.
A centrifugal pump converts energy of a prime mover (an electric motor or turbine) first
into velocity or kinetic energy and then into pressure energy of a fluid that is being pumped.
The energy changes occur by virtue of two main parts of the pump, the impeller and the volute
or diffuser. The impeller is the rotating part that converts driver energy into the kinetic energy.
The volute or diffuser is the stationary part that converts the kinetic energy into pressure energy.
All of the forms of energy involved in a liquid flow system are expressed in terms of feet of
liquid i.e. head.
The process liquid enters the suction nozzle and then into the eye (center) of an impeller.
When the impeller rotates, it spins the liquid sitting in the cavities between the vanes outward
and provides centrifugal acceleration. As liquid leaves the eye of the impeller, a low-pressure
area is created causing more liquid to flow toward the inlet. Because the impeller blades are
curved, the fluid is pushed in a tangential and radial direction by the centrifugal force. This
force acting inside the pump is the same one that keeps water inside a bucket that is rotating at
the end of a string.
The key idea is that the energy created by the centrifugal force is kinetic energy. The
amount of energy given to the liquid is proportional to the velocity at the edge or vane tip of the
impeller. The faster the impeller revolves or the bigger the impeller is, then the higher will be
the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid. This
kinetic energy of a liquid coming out of an impeller is harnessed by creating a resistance to the
flow. The first resistance is created by the pump volute (casing) that catches the liquid and
slows it down. In the discharge nozzle, the liquid further decelerates and its velocity is
converted to pressure according to Bernoulli‟s principle.
11
Theory:
If we consider the inlet and discharge of the pump under test as the boundaries of a
control volume then we may apply Bernoulli's Theorem of continuity to the fluid within that
boundary (Armfield, 1980).
The head generated by the machine is:
Machine Head = g Δ H
J/kg
(1)
where ΔH is the pump differential head (m) and g is gravitational acceleration 9.807 m/s2.
Hydraulic power:
The hydraulic power of the pump is the product of machine head and flow, thus hydraulic
Power Nh,
Nh = g•Q• Δ H•ρwater
W
(2)
where Q is the flowrate (m3/s) and ρwater is the density of water kg/ m3
Power Input to Pump:
The dynamometer output power (brake horsepower) No is given by:
No=T*n
W
where, T = dynamometer torque
n = dynamometer rotational speed
(3)
N-m
rad/s
60
nm = n * 2
2
n = nm * 60
RPM
(4)
rad/s
(5)
W
(6)
Substituting in equation (3):
2
No=T * nm* 60
The power absorbed by the pump therefore, is the dynamometer output less transmission losses,
thus:
N p = No- NL
W
12
(7)
NL represents the transmission losses between the pump and the dynamometer motor and is the
power absorbed by bearing friction, air drag, etc. The value of the power loss will vary
between rigs and on the same rig will vary with motor speed.
The efficiency of the pump:

Nh
No
 100%
(8)
Pump Differential Head:
The measurement of pump differential head is effected by means of the two Bourdon
type pressure gauges.
It should be noted that the suction and discharge pipes are of different nominal bores thus
generating a velocity head across the pump which must be accounted for when measuring the
differential head.
The differential head can be calculated:
Pd  Ps Vd2 Vs2
H 
[  ] Z
water g 2 g 2 g
m
(9)
where Ps is the pressure at the inlet of the pump; Pd is the pressure at the outlet of the pump; and
Z is the vertical difference between the inlet and outlet (negligible in this case). Vs is the
velocity at the inlet and Vd is the velocity at discharge (m/s).
From a mass balance:
Ds4
V 2  Vs2
d
D4
d
m2 / s 2
(10)
Pd  Ps Vs2 Ds4
H 
 [
 1]
 water g 2 g Dd4
m
(11)
(m/s)2
(12)
So,
In the case where:
Suction pipe NB, Ds=2.0"
Discharge pipe NB, Dd=1.5"
Since:
Vs2 
Q2
As2
where Q is the flowrate (m3/s) and As is the cross section area of the inlet pipe (m2).
then:
13
H 
Pd  Ps
Q 2 Ds4

[
 1]
 water g 2 gAs2 Dd4
m
(13)
Net Positive Suction Head (NPSH):
The net positive suction head is the equivalent total head of liquid at the inlet of the pump
(suction) (Hs) minus the vapour pressure p.
NPSH  H s 
p
g
(14)
Vs2
2g
(15)
Where:
Hs 
Ps
 water g

Pump Discharge
1. The basic method of measuring the pump discharge on the test rig is by means of the
volumetric measuring tank. The discharge is directed into the tank for a known period of time
and the rise in water level during that period noted, then:
Ad
Q=
m3/s
(16)
t
where A = area of measuring tank, m2
d = change in water level in tank, m
t = time, s
2. Venturi:
The pump discharge may be measured by means of the perspex venturi tube after the tube
has been calibrated. The venturi is being used in conjunction with a Dwyer Differential Pressure
transmitter.
The venturi demonstrates the principle of Bernoulli's continuity equation, thus flowrate Q
is related to the difference in pressure across the Venturi meter,
w  CA2
2 P  water
1  4
Kg/s
(17)
where A2 is the cross-sectional area of the throat of the Venturi, C is the Venturi coefficient, and
β is the ratio of throat diameter to inside pipe diameter (pump outlet pipe diameter for the case
being studied).
In the case of an actual venturi, small losses occur due to viscous shear and friction effects, thus
reducing the theoretical flow through the device into Equation (17). A calibration curve for a
14
particular venturi tube will therefore show curves of theoretical discharge, predicted by the
equation, and actual discharge determined by volumetric measurement.
Nomenclature:
A
As
D
H
Hatm
Hgs
Hgd
Hs
Hvs
ΔH
L
n
N
p
Q
t
T
V
W
d
w
Suffix:p
o
L
h
s
d
1, 2
Constants:
g
water
area of measuring tank m2.
cross section area of the inlet pipe, m2.
diameter of pipe, m
head, m
the barometer reading, m.
the reading of a gauge at the inlet of the pump, m.
the reading of a gauge at the outlet of the pump, m
the equivalent total head of liquid at the inlet of the pump
(suction), m
the velocity head at the inlet, m.
pump differential head, m.
length of dynamometer torque arm, m.
rotational speed rad/s.
power, w
the vapor pressure, mmHg
flowrate m3 /s
time, s.
torque kg-m
velocity. m/s.
weight applied to torque arm, Kg
change in water level in tank, m
flowrate Kg/s
pump input
dynamometer motor output
dynamometer transmission losses
hydraulic output
inlet (suction)
discharge
differential manometer limbs
Gravitational acceleration = 9.807 m/s2
density of water, 103 kg/ m3
15
Apparatus:
The centrifugal pump used in this experiment is the Armfield R2-00. The pump
is of cast iron construction and is provided with an open impeller. On the pump cover plate
tappings are provided at various radii so that the increase in pressure across the impeller may be
determined. These tappings are brought to a manifold with valves for pressure sampling as
required.
The pump is driven by a trunnion mounted variable speed 1.6 kW DC motor. The pump
set is mounted on a substantial bed plate. The equipment includes a combined
transformer/rectifier and speed controller.
The rig includes the tanks necessary for carrying out performance testing. The main
reservoir is approximately 1.36m x 0.66 m x 0.53 m fabricated in G.R P. and fitted with a drain
valve. On this tank is mounted the volumetric measuring tank which incorporate a level indicator
and scale. A quick acting drain valve is provided together with an emergency overflow. A
manually operated diverter is included so that water discharged by the pump can be returned
either directly to the sump or to the measuring tank as required. To carry out flow measurement
it is necessary for a stop watch to be used. This system allows level measurements to be taken in
still water and, hence, increases the accuracy of flow measurement.
The pump suction pipe is fabricated in PVC with pressure tapping. The pump delivery
pipe work incorporates a gate type throttle valve. Pressure and suction electronic indicators are
supplied complete with small bore pipe work and valves to allow multiple pressure readings.
A perspex Venturi uses pressure transmitters and indicators. This Venturi is modeled on
the requirements of B.S. 1042 Part 1- 1964 having a nominal bore of 1.5" and a throat diameter
of 1.28". The Venturi operates in conjunction with a 25 psi Dwyer differential transmitter and
Omega DP32 indicator. This instrument allows pump flows up to 60 GPM (5 L/sec.) to be
determined, after the instrument has been calibrated.
A 50 psi Differential Pressure
transmitter is also available. This instrument allows the differential heads developed by the
pump up to 30 ft to be determined. Tappings are provided on the pump and the supply includes
all necessary fittings and connecting flexible tube.
Specification:
Inlet pipe diameter
Outlet pipe diameter
Venturi throat diameter
Impeller outside diameter
Blade width
Number of blades
Blade type
Impeller type
Radius of strain gauge
2.0"
1.5"
1.28"
127 mm
11.4 mm
6
Backward curving
Open
1144.2 mm
16
Shaft Speed
Rating
Motor type
Electrical Supply
0 - 3000 RPM
1.6 kW at 2900 RPM.
Variable speed
220V/single phase/50-60 Hz
Relationship between Torque and voltage for strain gauge (when using x 10
amplification):
Torque=1.5861*Volts*g*0.1442
Procedure:
Start up Procedure
a) Be sure suction side and discharge side valves are closed.
b) Turn on Main Power.
c) Turn on priming pump and slightly open discharge valve.
d) Adjust pump speed to approximately 15%.
e) Open suction side valve SLOWLY. Repeat as necessary.
f) Open discharge side valve SLOWLY.
g) Turn the Venturi Drain valve until line is drained of air.
h) Turn the Pressure Guage Drain(s) to Vent until the line is drained of air, and then
turn the valve to the right until suction lines are airless. Then turn valve to Suction so
the line is static.
Shut Down Procedure
a)
b)
c)
d)
Close discharge side valve.
Close suction side valve.
Reduce motor speed to 0 RPM using controller.
Switch motor off.
Experimental Procedure
a) Calibrate the venturi meter by making at least 8 runs from a low flowrate to a high
flowrate. The venturi meter is calibrated using the measuring tank and stopwatch.
b) At 8 or more discharge rates collect the data necessary to characterize the pump
including the pressures across the pump, venturi pressure drop, motor rotating speed
and the Torque Gauge Reading.
17
Report:
1) To determine various characteristics and parameters of a centrifugal pump. These
include graphs of total pump differential head, hydraulic power, brake horse power, efficiency
and Net positive suction power versus discharge flowrates.
2) To determine the size of a geometrically similar pump that would be needed to pump
against a total head of 100 feet of water at peak efficiency using the same RPM. What flowrate
is generated by the big pump at this condition? If energy costs 10.2 cents/kw-hr, how much
does it cost to operate the big pump each year?
References:
Armfield Technical Education Co. Ltd., “Instructional Manual for Centrifugal Pump Test Rig
R2-00”, 1980.
Other references related to this lab:
Perry, R. H., Green, D. W. and Maloney J. O., “Perry‟s Chemical Engineering Handbook”,
McGraw-Hill, 1997.
Sulzer Pump Division, Sulzer Brothers Ltd., “Sulzer centrifugal pump handbook”, Elsevier
Applied Sicence, London and New York, 1989.
Lobanoff, V. S. and Robert, R. R., “Centrifugal Pumps – Design & Application”, Gulf
Publishing Company, Houston, 1985.
Karassik, I. J., “Centrifugal Pump Clinic”, Dekker, New York, 1989.
Brown, G. G., “Unit Operation”, Wiley, New York, 1950.
Coulson, J.M. and Richardson, J. F., „Chemical Engineering” Vol. 1. 3rd Edition, p.133-144,
1977, (TP145C45).
.
18
3.
Fluid Metering
Introduction
In this experiment you will be measuring the flow rate of water which is pumped through a loop,
using a variety of flowmeters as listed below:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Magnetic Drive
Nutating Disc
Coriolis
Torsion Paddle
3 Beam Ultrasonic
Vortex
Altometer (Enviromag)
Variable Area (Rotameter)
Venturi
Orifice
Doppler Ultrasonic
V-notch Weir
You may use the readings from the Coriolis flow meter as the standard value. Compare the
reading of other flow meters with this value and discuss the observed differences, if any. Using
the values of flow rates obtained by the Coriolis Meter, determine the meter coefficients for the
Orifice and Venturi meters as functions of Reynolds number. These can be compared to the
expected values found in the literature.The Magnetic flowmeter readings should be linear with
flow rate. Evaluate the magnetic flowmeter coefficient for converting EMF to flow rate. The
Ultrasonic meter should also give a linear signal with respect to flow rate. Examine your
readings with the ultrasonic meter to see if such linear relationship can be established.
In your reports review the operating principles of each flow meter, compare their advantages and
disadvantages and comment on the practical applications for each device.
Finally,
consider the following situations and suggest a suitable flowmeter for each case. The factors to
be considered are capital cost (including data processing), operating cost (primarily energy
losses), reliability (whether calibration is required or not).
a)
b)
c)
d)
e)
f)
g)
measuring the flow of water into households
measuring the flow of water in a 5 foot diameter pipe
measuring the flow of heavy crude oil in a 3 inch pipe
measuring the flow of coal-water in a 12 inch pipe
measuring the flow of water into a laboratory reactor
measuring the flow of water in a small creek
measuring the flows of petroleum derivatives in an automated refinery
19
Some background information is given in References 1, 2, 3.
Procedure
Determine the direction the water flows and decide how you will adjust the flow rate. Be sure to
start your measurements at a low flow rate and then increase between readings. Determine
where each meter is located and how to make a measurement for it (discuss this with the TA).
Note that for the Orifice and Venturi meters you have to make pressure measurements and this is
accomplished with a pressure transducer. The transducers will need to have the air removed and
the associated demodulators will have to be zeroed. Confirm this procedure with your TA before
adjustments are made. Make at least eight measurements by first increasing the flow rate and
then reducing it to zero.
Calculations
(1) Orifice or Venturi: The flowrate Q is related to the pressure drop, minimum (throat) area and
density  by the equation:
Q  CA
2P
(1   4 )
where C is the coefficient of discharge.
(2) V-Notch Weir:
Q (0.31h02.5 2 g ) / tan
Where ho is the height of the liquid above the bottom of the weir and  is the angle between
the side of the notch and the horizontal.
Data
Diameter of pipe
Diameter of orifice
Diameter of venturi
Angle of weir
=
=
=
=
1.049 in.
0.441 in.
0.33 in.
54o
References
1. N. de Nevers, Fluid Mechanics for Chemical Engineers, 3rd Ed. McGraw Hill (2005).
2. J. O. Wilkes, Fluid Mechanics for Chemical Engineers, 2nd Ed. Prentice Hall (2006).
3. Y. A. Cengel, J.M. Cimbala, Fluid Mechanics: Fundamentals and Applications.
McGraw Hill (2006).
20
4. Saturation Pressure
Objectives
1. To describe the relationship between pressure and temperature of fluid vaporization.
2. To investigate the accuracy of saturation data obtained using basic equipment.
Learning Outcomes
At the end of this laboratory session, students should be able to:
1. Plot a relationship between pressure and temperature of fluid vaporization.
2. Apply interpolation technique.
3. Explain the effect of saturation line through the changes of pressure level.
Theory
It is commonly understood that the temperature at which water undergoes a liquid-to-vapour
phase change varies with pressure. For example, water boils at a lower temperature when at high
altitudes, such as encountered on mountains. This relationship between pressure and temperature
at which the liquid-to-vapour phase change occurs may be plotted on a graph. The resulting line
is termed the saturation line. Saturation lines may be obtained for any fluid, although in this
experiment water will be used. When plotted on a graph of absolute pressure Pabs against
absolute temperature Tabs, the result is a smooth curve. The curve does not have a simple
describing equation, but over a limited range of pressure it is possible to obtain a good fit using:
(1)
This equation is not derived from any theory or underlying physical laws. It only describes
behavior. For any particular range of pressures, there are particular values of the coefficients a
and p0 which minimize the differences between the measured points and the
curve given by the equation. These differences arise both through experimental errors
(random, scale and zero errors) and because the real behavior does not perfectly match
the describing equation. Obtaining best-fit values of the coefficients a and p0 may only be
obtained by linearizing the curve. The usual method for doing this is to take logarithms of
Equation (1):
(2)
Therefore a and ln p0 are respectively, the gradient and the intercept of a graph of ln Pabs
vs. (1/T).
21
Apparatus
Figure 1- TH3 Saturation Pressure Apparatus.
Apparatus Set-Up
1. Check the water level, until the water level is halfway up the sight-glass (6) at front
of the boiler.
2. If water level is low, open the filling valve and fill the apparatus using purified or de-ionized
water in filling point, until the water level is halfway up the sight glass at the front of the boiler.
Seal the filling valve after sufficient amount of water stored in the boiler with the key.
Procedures
A. Pressure Increase
1.
2.
3.
4.
Turn on the computer and data logger.
Switch ON the heater and turn the heater volume control to maximum.
Close the isolating valve.
Allow the water to heat up until 1 bar, record the resistance as shown in the data logger.
• Pressure - refer at view diagram
22
• Measured resistance - refer at data logger
5. For pressures of 2 bar-7 bar, repeat step 4 to record the corresponding resistance.
6. Use the PT100 Platinum Resistance Thermometer Reference Chart to find the
temperature at the measured resistance. Use an interpolation technique if necessary.
B. Pressure Decrease
1. Switch OFF the heater, and turn the heater volume control to minimum after the pressure
reaches 7 bar.
2. Slowly open the isolating valve.
3. As the pressure drops, repeat step 4 as in the Pressure Increase experiment. Record the
measured resistance values accordingly.
4. For temperature data, repeat step 6 as in the Pressure Increase experiment.
5. Switch off the data logger main switch and turn off the computer after completing the
experiment.
Notes
AFTER THE DATA HAS BEEN TAKEN, LEAVE THE CALORIMETER ISOLATING
VALVE OPEN, HEATER POWER OFF AND HEATER CONTROL MINIMUM AND
TURN OFF COMPUTER
23
5.
HEAT EXCHANGE – Double Pipe (W/W)
Purpose
To determine the heat transfer rates and coefficients for a
exchanger
Double Pipe - (water-water) heat
Each evaluation should consist of a check on the enthalpy balance and a comparison of
experimental and literature values of heat transfer coefficients. Some discussion of pressure drop
may also be appropriate.
Reading
Fairly extensive (but not very difficult) reading will be necessary before you do the experiment
so that you will be able to do a good job and understand what is involved. Read (if you have not
already done so) the following sections in the book by Incropera et al.: 1.2.2, 6.1, 7.1, 8.5, 11.1,
11.2, 11.3.
Background
Cross-flow heat exchangers involve fairly complex flow patterns. Of course the flow pattern
affects the rate of heat transfer. A common approach is to calculate transfer coefficients from
empirical correlations, combine resistances in series at steady state, calculate a logarithmic mean
T for counter-current flow, find a correction factor for the complex flow pattern, and to
combine factors to give the heat transfer rate. This is the LMTD-correction factor method.
The equations for the counter-flow heat exchanger are 11.14, 11.15 and 11.17 with Fig. 11.8.
The mean T for the complex flow pattern is given by:
Tm = F(T)lm,CF
where F is given by Figures 11.10 to 11.13. The subscript lm indicates logarithmic mean and CF
denotes a hypothetical counterflow exchanger.
Theory
Generally speaking, three types of heat transfer mechanisms are thought to exist:
Conduction - occurs by molecular transport in the presence of a temperature gradient
Convection - occurs by molecular or bulk motion of a fluid in the presence of a
temperature gradient
24
Radiation -
occurs by energy transmission from matter in the presence of a
temperature difference.
In these experiments, students will be investigating primarily convective heat transfer
mechanisms. This mechanism is the most commonly found in the chemical industry.
The object of the experiments will be to measure the overall resistance to heat transfer at
different operating conditions and compare these measurements to those predicted by equations
in the literature.
When a fluid flows over a surface which is at a different temperature than the fluid, then the
local heat transfer flux is:
dq
 hx Ts  TF 
dA
Where q
A
hx
TS
TF
=
=
=
=
=
heat transfer rate
surface area
local heat transfer coefficient
surface temperature
fluid temperature
Because the flow conditions may change with position, the local heat transfer coefficient is not
constant in the above process. Also, as the fluid and/or solid changes temperature, TS – TF will
not be constant. Thus the precise determination of the overall heat transfer rate would require an
integration of the form:
q

OUT
dq 
IN

OUT
hx TS  TF dA
IN
Because this would be a difficult (if not impossible) equation to solve for practical heat
exchanger situations, engineers have simplified it to an algebraic equation.
q = h A T1m
… where T1m = log mean temperature difference
h
= individual heat transfer coefficient
The individual heat transfer coefficient is not a constant but depends on velocity and
temperatures. Ranges of h can be found in Bennett & Myers (Table 21-1). The log mean
temperature difference between the surface and fluid is computed by an equation of the type:
TB1IN
TB2OUT
TSI
TS2
25
T1m 
T  T   T
ln T  T  T
S1
B1IN
S1
S2
B1IN
S2
 TB2OUT


 TB1OUT
In real heat exchange processes, heat is often transferred from one fluid to another through a
solid medium. Often this solid medium is corroded or contains a layer of solid deposits. Thus
the heat transfer rate is now given by an equation of the form:
q = Uo Ao T1m
And:
Uo 
where: Uo
hi
hdi
kw
xw
ho
hdo
Ao
AI
A1m
Ao
Ao

Ai hi
Ai hdi
=
=
=
=
=
=
=
=
=
=
1
Ax
1
1
 o w 

A1m k w ho
hdo
overall heat transfer coefficient
inside fluid heat transfer coefficient
inside fouling heat transfer coefficient
thermal conductivity of wall
thickness of wall
outside fluid heat transfer coefficient
outside fouling heat transfer coefficient
outside heat transfer area
inside heat transfer area
log mean heat transfer area
Empirical equations exist for hI and ho and depend on dimensionless parameters such as
Reynolds number and Prandtl number. Correlations can be found in the references listed at the
end of this preamble.
In this case, the evaluation of the log mean temperature difference depends on the direction of
flow of the fluids. For countercurrent flow it is given by:
TB1, OUT
TB1, IN
TB2, IN
TB2, OUT
26
T1m 
TB 2, IN  TB1, OUT  TB 2, OUT  TB1, IN 
 TB 2, IN  TB1, OUT
ln 
 TB 2, OUT  TB1, IN





Finally, we have another complication for real heat exchangers. If the fluids are not in parallel
flow but there is some cross-flow or combination of concurrent flow and countercurrent flow,
(multipass heat exchangers) then a correction factor must be put in the above equation:
q = UoAY T1m
Where Y = correction factor
Y values are dependent on the type of heat exchanger and temperature driving forces. They are
available in graphs in the references listed at the end of this preamble.
In your heat exchange experiments, you measure the temperatures of the fluids, and their flow
rates. The heat transfer rate can then be calculated by:
q2 = MCP2 (TB2, IN - TB2, OUT)
where M = mass flowrate of fluid 2
CP2 = heat capacity of fluid 2
Procedures
1. The flow rates of the fluids can be controlled by adjustment of appropriate valves.
2. Sufficient time must be allowed for the system to come to steady state before measurements
are made. In your report, indicate how you knew that steady state has been achieved. How
much time was required?
3. Measurements are made of temperatures using thermistors and flow rates using calibrated
meters.
4. Several different operating conditions (flow rates, etc.) should be studied in order to obtain as
much information as possible to characterize the system. Discuss choice of operating
conditions with your demonstrator.
27
5.
Heat transfer rates, heat transfer coefficients, pressure losses and energy losses should all be
evaluated if possible and compared to values and/or trends reported in the literature.
6. When heat balances are of interest, be sure that the temperature differences for the streams
can be determined reasonably accurately.
Report: In your write-up, report the heat transfer rates and coefficients for the exchanger that
you studied and discuss the problem of scaling up your heat exchanger to allow for a one
hundred fold increase in flowrate of the cold fluid but still maintain the same temperature rise.
References:
1. Bennett, C.O. and J.E. Myers, “Momentum, Heat, and Mass Transfer”, McGraw Hill Book
Co., 1982.
2. Incropera, F.P. and D.P. Dewitt, “Fundamentals of Heat Transfer”, John Wiley & Sons,
1981.
3. Perry, R.H., “Perry‟s Chemical Engineers‟ Handbook, McGraw-Hill Book Co., 1985.
Equipment Data
Tube 1: OT Cu – IT Cu
Tube 2: OT Cu – IT Cu
Tube 3: OT Cu – IT SS
Tube 4: OT Cu – IT Cu
Tube 5: OT Cu – IT Cu
Tube 6: Air – not used
OT: 1” Cu Pipe, OD = 1.134”
ID = 0.994”
IT: ½” Cu Pipe, OD = 0.63”
ID = 0.534”
IT: ½” SS Pipe, OD = 0.63”
ID = 0.546”
IT: ¾” Cu Pipe, OD = 0.881”
ID = 0.772”
28
29
30
6. FLUID FRICTION IN PIPES, VALVES AND FITTINGS
A variety of studies will be conducted with this equipment, including the determination of:
a) the friction factor - Reynolds number relationship for pipe flow,
b) valve coefficients (Cv values) and characteristics (f(x) vs x) for gate valves, and globe
valves,
c) friction losses for various fittings.
Since the piping systems used for a, b, and c contain substantial lengths of pipe, it will be
necessary to correct the measured pressure drops for the lengths of straight piping between the
fittings. These corrections should be calculated assuming the pipe is smooth.
The main apparatus is a flow loop with ten (10) separate lines, each incorporating different types
of fittings. The pressure differences across the piping and from the venturi meter are measured
with variable reluctance differential pressure transducers.
The transducer output is a voltage signal that is collected by Voltage Meters and Demodulators,
which are connected to a SCB-68 National Instruments Shielded I/O Connector Block for DAQ
Devices with 68-pin connectors. The Connector Block is then used to send voltage signals to a
NI PCI-MIO-16E-4 I/O Terminal installed in an IBM Intel computer. The resulting signals are
then picked up by LabVIEW 8.2 and displayed in “Fluid Friction.vi” in a series of graphs and
indicators. A cold junction-compensated (CJC) thermocouple is used to measure the temperature
of the fluid. The CJC occupies channel ai0 and the thermocouple is attached to channel ai1 and
ai9 of the connector block.
Each transducer is calibrated individually. The Demodulators are set to zero by allowing the
individual transducers to be open to atmospheric pressure (with both bleed screws open). Once
stabilized, the spans of the Demodulators are set at 10V with the bleed screws closed and air
applied at the appropriate pressure. The exact procedure will be discussed by the TA.
To measure the flow rate for comparison with the venture meter, a bucket, stopwatch, and scale
are required. A 3/32” Allen wrench is also necessary for adjusting the pressure transducer bleed
screws. The inside diameter of the tubing is 0.527 inches.
The equipment is fairly complex and you will have to spend some time tracing the flow lines and
thinking about what you are going to do. Don‟t turn anything on until the demonstrator has
given his/her approval.
From your experimental measurements on the Venturi meter, calculate the coefficient of
discharge, C, in the relation:
31
w  CA 2
2 (  p )1
1  4
where W is the mass rate of flow,
A2 is the cross-sectional area of the throat of the Venturi,
1 is the density of the fluid just upstream of the throat,
(-) is the pressure difference across the Venturi,
 is the ratio of throat diameter to inside pipe diameter (14.3 mm and 25.3 mm
respectively)
The valve coefficient and valve stem function are defined as:
Q  Cv f ( x)
where
Q
Cv
f(x)
S
Pv
x
Pv
S
= flowrate (US gallon/minute)
= valve coefficient (usgpm/psi0.5)
= dimensionless stem function (0, closed; 1, fully open)
= fluid density/water density
= pressure drop over valve (psi)
= stem position (fraction open)
A possible f(x) vs x relationship is of the form f(x) = xm.
In examining the valve performances the data should be used to find best-fit values of Cv and m.
Losses for flow through fittings larger than 1 inch in diameter are given in References 1 and 2.
References
1. Anon, “Flow of Fluid Through Valves, Fittings and Pipe”, Technical Paper No. M-409,
Crane Ltd., 1950.
2. Perry‟s Chemical Engineers‟ Handbook, 6th Edition, 1984.
32